Added try/except to adr_controller to raise (and handle) ValueErrors during the function_loop of adr_controller.

Added error handling for conversion from string to float in data logger.

The method set_pid_manual_out() added to the server, which allows the controller to actually perform mag_up and mag_down. For the future remember to add comm.send('xyx') first.

Note that self.length in data_logger should be made more elegant. Perhaps use len(time_dim) instead or len(own list) to get the index. (Problem: can't constantly do that or I will increase the length once for each data point).